Has anyone played with it? Are the backends hierarchical (can you store stuff in multiple backends)? Are they pluggable (can you add a new storage backend e.g. to a remote system or a shared webworker)?
Last month attempted to integrate it into a product that needed something in between local storage and IndexedDB. All the fallbacks worked perfectly. But the lack of an index (and therefore the inability to do bulk reads) was a deal-breaker. I ended up going for IndexedDB with a WebSql-based polyfill.
You could easily add your own backend relatively easily (the API is easy to copy), though it's not really "optimized" for that yet. It's designed with offline storage for JS in mind though, so the library itself likely won't support remote calls.